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authorPaolo Valente <paolo.valente@linaro.org>2017-05-09 11:37:27 +0200
committerJens Axboe <axboe@fb.com>2017-05-10 07:39:43 -0600
commita66c38a171ed25488debf80247a9e72e1026e82c (patch)
tree52c407a83f2706d34e5ced556903bcb5939265dc
parentfba704b494fdc6816a039a66887274b4e5c00eeb (diff)
downloadlinux-a66c38a171ed25488debf80247a9e72e1026e82c.tar.bz2
block, bfq: use pointer entity->sched_data only if set
In the function __bfq_deactivate_entity, the pointer entity->sched_data could happen to be used before being properly initialized. This led to a NULL pointer dereference. This commit fixes this bug by just using this pointer only where it is safe to do so. Reported-by: Tom Harrison <l12436.tw@gmail.com> Tested-by: Tom Harrison <l12436.tw@gmail.com> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@fb.com>
-rw-r--r--block/bfq-wf2q.c13
1 files changed, 11 insertions, 2 deletions
diff --git a/block/bfq-wf2q.c b/block/bfq-wf2q.c
index b4fc3e4260b7..8726ede19eef 100644
--- a/block/bfq-wf2q.c
+++ b/block/bfq-wf2q.c
@@ -1114,12 +1114,21 @@ static void bfq_activate_requeue_entity(struct bfq_entity *entity,
bool __bfq_deactivate_entity(struct bfq_entity *entity, bool ins_into_idle_tree)
{
struct bfq_sched_data *sd = entity->sched_data;
- struct bfq_service_tree *st = bfq_entity_service_tree(entity);
- int is_in_service = entity == sd->in_service_entity;
+ struct bfq_service_tree *st;
+ bool is_in_service;
if (!entity->on_st) /* entity never activated, or already inactive */
return false;
+ /*
+ * If we get here, then entity is active, which implies that
+ * bfq_group_set_parent has already been invoked for the group
+ * represented by entity. Therefore, the field
+ * entity->sched_data has been set, and we can safely use it.
+ */
+ st = bfq_entity_service_tree(entity);
+ is_in_service = entity == sd->in_service_entity;
+
if (is_in_service)
bfq_calc_finish(entity, entity->service);